skb: make drop reason booleanable

We have a number of cases where function returns drop/no drop
decision as a boolean. Now that we want to report the reason
code as well we have to pass extra output arguments.

We can make the reason code evaluate correctly as bool.

I believe we're good to reorder the reasons as they are
reported to user space as strings.
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Reviewed-by: David Ahern <dsahern@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/skbuff.h

@@ -314,6 +314,7 @@ struct sk_buff;
  * used to translate the reason to string.
  */
 enum skb_drop_reason {
+	SKB_NOT_DROPPED_YET = 0,
 	SKB_DROP_REASON_NOT_SPECIFIED,	/* drop reason is not specified */
 	SKB_DROP_REASON_NO_SOCKET,	/* socket not found */
 	SKB_DROP_REASON_PKT_TOO_SMALL,	/* packet size is too small */

include/net/tcp.h

@@ -1674,8 +1674,9 @@ tcp_md5_do_lookup(const struct sock *sk, int l3index,
 		return NULL;
 	return __tcp_md5_do_lookup(sk, l3index, addr, family);
 }
-bool tcp_inbound_md5_hash(const struct sock *sk, const struct sk_buff *skb,
-			  enum skb_drop_reason *reason,
+
+enum skb_drop_reason
+tcp_inbound_md5_hash(const struct sock *sk, const struct sk_buff *skb,
 		     const void *saddr, const void *daddr,
 		     int family, int dif, int sdif);
 
@@ -1688,13 +1689,13 @@ tcp_md5_do_lookup(const struct sock *sk, int l3index,
 {
 	return NULL;
 }
-static inline bool tcp_inbound_md5_hash(const struct sock *sk,
-					const struct sk_buff *skb,
-					enum skb_drop_reason *reason,
+
+static inline enum skb_drop_reason
+tcp_inbound_md5_hash(const struct sock *sk, const struct sk_buff *skb,
 		     const void *saddr, const void *daddr,
-					int family, int dif, int sdif)
+		     int family, int dif, int sdif);
 {
-	return false;
+	return SKB_NOT_DROPPED_YET;
 }
 #define tcp_twsk_md5_key(twsk)	NULL
 #endif

net/ipv4/tcp.c

@@ -4434,8 +4434,8 @@ int tcp_md5_hash_key(struct tcp_md5sig_pool *hp, const struct tcp_md5sig_key *ke
 EXPORT_SYMBOL(tcp_md5_hash_key);
 
 /* Called with rcu_read_lock() */
-bool tcp_inbound_md5_hash(const struct sock *sk, const struct sk_buff *skb,
-			  enum skb_drop_reason *reason,
+enum skb_drop_reason
+tcp_inbound_md5_hash(const struct sock *sk, const struct sk_buff *skb,
 		     const void *saddr, const void *daddr,
 		     int family, int dif, int sdif)
 {
@@ -4464,18 +4464,16 @@ bool tcp_inbound_md5_hash(const struct sock *sk, const struct sk_buff *skb,
 
 	/* We've parsed the options - do we have a hash? */
 	if (!hash_expected && !hash_location)
-		return false;
+		return SKB_NOT_DROPPED_YET;
 
 	if (hash_expected && !hash_location) {
-		*reason = SKB_DROP_REASON_TCP_MD5NOTFOUND;
 		NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPMD5NOTFOUND);
-		return true;
+		return SKB_DROP_REASON_TCP_MD5NOTFOUND;
 	}
 
 	if (!hash_expected && hash_location) {
-		*reason = SKB_DROP_REASON_TCP_MD5UNEXPECTED;
 		NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPMD5UNEXPECTED);
-		return true;
+		return SKB_DROP_REASON_TCP_MD5UNEXPECTED;
 	}
 
 	/* check the signature */
@@ -4483,7 +4481,6 @@ bool tcp_inbound_md5_hash(const struct sock *sk, const struct sk_buff *skb,
 						 NULL, skb);
 
 	if (genhash || memcmp(hash_location, newhash, 16) != 0) {
-		*reason = SKB_DROP_REASON_TCP_MD5FAILURE;
 		NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPMD5FAILURE);
 		if (family == AF_INET) {
 			net_info_ratelimited("MD5 Hash failed for (%pI4, %d)->(%pI4, %d)%s L3 index %d\n",
@@ -4497,9 +4494,9 @@ bool tcp_inbound_md5_hash(const struct sock *sk, const struct sk_buff *skb,
 					saddr, ntohs(th->source),
 					daddr, ntohs(th->dest), l3index);
 		}
-		return true;
+		return SKB_DROP_REASON_TCP_MD5FAILURE;
 	}
-	return false;
+	return SKB_NOT_DROPPED_YET;
 }
 EXPORT_SYMBOL(tcp_inbound_md5_hash);
 

net/ipv4/tcp_ipv4.c

@@ -1965,9 +1965,10 @@ int tcp_v4_rcv(struct sk_buff *skb)
 		struct sock *nsk;
 
 		sk = req->rsk_listener;
-		if (unlikely(tcp_inbound_md5_hash(sk, skb, &drop_reason,
+		drop_reason = tcp_inbound_md5_hash(sk, skb,
 						   &iph->saddr, &iph->daddr,
-						  AF_INET, dif, sdif))) {
+						   AF_INET, dif, sdif);
+		if (unlikely(drop_reason)) {
 			sk_drops_add(sk, skb);
 			reqsk_put(req);
 			goto discard_it;
@@ -2041,8 +2042,9 @@ int tcp_v4_rcv(struct sk_buff *skb)
 		goto discard_and_relse;
 	}
 
-	if (tcp_inbound_md5_hash(sk, skb, &drop_reason, &iph->saddr,
-				 &iph->daddr, AF_INET, dif, sdif))
+	drop_reason = tcp_inbound_md5_hash(sk, skb, &iph->saddr,
+					   &iph->daddr, AF_INET, dif, sdif);
+	if (drop_reason)
 		goto discard_and_relse;
 
 	nf_reset_ct(skb);

net/ipv6/tcp_ipv6.c

@@ -1632,8 +1632,10 @@ INDIRECT_CALLABLE_SCOPE int tcp_v6_rcv(struct sk_buff *skb)
 		struct sock *nsk;
 
 		sk = req->rsk_listener;
-		if (tcp_inbound_md5_hash(sk, skb, &drop_reason, &hdr->saddr,
-					 &hdr->daddr, AF_INET6, dif, sdif)) {
+		drop_reason = tcp_inbound_md5_hash(sk, skb,
+						   &hdr->saddr, &hdr->daddr,
+						   AF_INET6, dif, sdif);
+		if (drop_reason) {
 			sk_drops_add(sk, skb);
 			reqsk_put(req);
 			goto discard_it;
@@ -1704,8 +1706,9 @@ INDIRECT_CALLABLE_SCOPE int tcp_v6_rcv(struct sk_buff *skb)
 		goto discard_and_relse;
 	}
 
-	if (tcp_inbound_md5_hash(sk, skb, &drop_reason, &hdr->saddr,
-				 &hdr->daddr, AF_INET6, dif, sdif))
+	drop_reason = tcp_inbound_md5_hash(sk, skb, &hdr->saddr, &hdr->daddr,
+					   AF_INET6, dif, sdif);
+	if (drop_reason)
 		goto discard_and_relse;
 
 	if (tcp_filter(sk, skb)) {